Well, Dofus does work pretty well. I played it for almost 6 months, which is the longest I've played any MMO and twice as long as I played WoW. Are you more interested in hearing what aspects of Dofus are problems and could be improved on, or what aspects of Dofus work and why, or what?

A bit of both would be best, honestly. I'm more focused on the flaws though. It seems to be easier to fix the flaws and make a better game than to out right copy one. Although if I knew what made Dofus do real well, I'd try and follow a similar suit because, hell, it works. I didn't want to focus this over one game though. I wanted to apply these questions to the genre as a whole. Sadly, there aren't that many games, so my selections are pretty limited for examples.

I'm personally interested in designing tactical combat games, MMO or otherwise. (I'd also like to play a new MMO with combat similar to Dofus'.) As far as I could find out there just is no other MMO with that kind of tactical combat. There are some great tactical single-player games, like the Disgaea series; there are small-scale multiplayer tactical games which don't have an RPG structure around them. But there aren't any directly-comparable MMOs. The closest are ones which have turn-based combat ala Final Fantasy where the player's characters are positioned in ranks but there is no movement on a chessboard-like battlefield, or ones which have constructed deck CCG combat. But the up side is that the non-combat part of Dofus is very standard with other MMOs, and the combat part of Dofus is pretty standard with single player tactical games.

As for what makes Dofus' combat work, I'd say the speed at which the combat happens is the single most important factor, while the variety of monster abilities is what keeps it from getting boring in the long term, and the comedy attitude is the main thing that makes the game's content apealing and memorable. What doesn't work about the combat, well personally I think the max group size of 8 is too big and the fact that most classes are built around controlling a single unit is boring. Only the ones with multiple summons and a mix of long range and short range spells are particularly interesting to play, plus sram with their traps and invisibility, but sram play is problematic to mix with other classes' play in a group. I could go on and on about what doesn't work about the non-combat parts of the game, same as any MMO.

Tactic games and MMOs do not mix well because their core elements are incompatible.

Tactic games are about building a squad of units with specific roles to create synergies and using these units according to a higher level plan. The number of actions each unit can do is inversely proportional to the number of units in play to keep overall complexity manageable. They make up for the lack of choice per unit turn by making the player build a higher level strategy by controlling multiple units. Also, the gameplay is generally turn based, which means there are pauses when the other player is moving his units.

MMOs are about the social interactions between you and the rest of the server. For them to work, you need to encourage the player to interact with other players.

The problem with a Tactic MMO is the unit complexity and active player time. You can go the standard MMO route where each player controls 1 unit. In this case, players will wait 90% of the time for their turn for others to do their actions, which is uninteresting.

The other way to go is to give the player a few units to control. This fixes the downtime issue and adds more choices to the player. The problem then becomes social interaction. You cannot have 6 players in the same group each controlling 3~5 units because that would slow down gameplay. You need to limit the party size to 3~4 depending on how many units each player controls. It becomes almost impossible to do large scale events because of this limitation, so the social aspect takes a hit and you end up with some players never interacting with anyone else except their close friend group. If a community can't build around this, then the MMO will fail.

I don't agree. Most MMO socialization does not take place during combat. You can have strong online communities built up around single-player and 2-player non-MMO games, all you have to do is incorporate a forum or chat channel as part of the game or linked to from the game. Dofus itself would not fail if max party size were suddenly changed from 8 to 3, as long as dungeons were scaled down to match (if anything it would improve the dungeons, many of which are gruelingly long to try to keep 8 people coordinated for). Guilds don't have to be about running dungeons, I've seen guilds which were primarily about other game aspects like collecting, focus on a minigame like fishing or pet/mount breeding, mentoring newbies, or dueling/fight club.

You're right that socialization can happen without combat, but it helps meeting new people. Also, why would players pay a monthly fee or stuff in a cash shop to chat with other players who are also paying? Might as well go to IRC and chat there. The game needs to be solid for that to happen and MMOs generally provide a worse playing experience than single player games, so you need to compensate with social gameplay. A chat channel is not enough in my opinion.

Well, all MMOs have a core of single player content. A fairly wide range of balances between single player and multiplayer content can be successful. I've played games with 90% single-player content that were quite successful as MMOs, including earning sizeable subscription and/or cash shop income. I personally avoid the ones that advertise being more than 30% multiplayer content (because other players are often the worst thing about an MMO) but I hear that extremely social MMOs are also successful. A tactical MMO might be inherently more on the single-player end of the spectrum, but it can be successful there. A mostly single-player game where your friend is playing the same game nearby, talking to you about what you are doing, trading you stuff, and can duel against you, is MMO enough to be a clear improvement on a single player game.

Rather that remove units from a party I'd have units normally be summoned into each battle by players. The choice of which units to summon is a tactical choice. There could be a max number of summons allowed per battle, divided by the number of players in the group to give a max number of summons per player. If you wanted to have parties of up to 4 people, 12 is the smallest number of units that would divide evenly by any party size. Or, you could have a variable number of max summons depending on what was being battled, and the summons could be doled out one per play until they ran out, with the player who gets to go first rotating within the party (similar to a loot distribution system).